Direction of coiling (torsion) in snails

Just recently I've been getting a load of emails from students in the US using my snail page, I'm sure there are loads better pages around, so I don't know why they like mine. Perhaps it's the mating pics. Anyway I decided to clear something up, and that is how to tell the difference between dextral and sinistral coiling.  So I drew a diagram showing the difference as my written explanation wasn't very good.  And here it is.

I don't like the word sinistral as it comes from the same old word as sinister, and has negative meanings.  But is used for left-handed people, of which I am one.